The present invention relates to a hermetic compressor which is improved such that a lubricating oil remains on the surface of a journal of a rotating shaft of the compressor when the compressor stops its operation.
A hermetic compressor is generally employed in a cooling system such as a refrigerator or an air conditioner, so as to compress a gaseous refrigerant from an evaporator to a high-temperature and high-pressure state and supply the compressed refrigerant to a condenser. The hermetic compressor generally includes a hermetic casing, a driving motor installed inside the casing and a compressing portion driven by the driving motor to compress the refrigerant. The compressing portion is classified into a reciprocating type and a rotary type according to its compression mechanism.
FIG. 7 shows a sectional view of a conventional hermetic reciprocating compressor. As shown in the drawing, the conventional compressor includes a casing 100 forming a closed internal space, a driving motor 101 installed inside the casing 100 and a compressing portion 130 which is driven by the driving motor 101.
The driving motor 101 includes a stator 102, a rotor 104 rotatably installed inside the stator 102 and a rotating shaft 106 fitted into the rotor 104 and rotating therewith.
The compressing portion 130 includes a cylinder 131, a piston 132 reciprocating inside the cylinder 131 and a cylinder head 133. The piston 132 is connected to an eccentric portion 112 of the rotating shaft 106 by a connecting rod 134 and reciprocates inside the cylinder 131 according to a rotational movement of the rotor 104, thereby inhaling and compressing the refrigerant.
A journal 109 is formed at the lower portion of the rotating shaft 106 and rotatably supported by a bearing 108. The journal 109 slides frictionally against the bearing 108. A lubricating oil 118 is contained in the bottom portion of the casing 100 and picked up by an oil pickup tube 116 which is extended downwardly from the eccentric portion 112 of the rotating shaft 106 to be supplied between the journal 109 and the bearing 108. The oil picked up by the oil pickup tube 116 flows upward along an oil groove 110 formed on the outer surface of the journal 109 and is supplied to the surface of the journal 109, so as to perform a lubricating action between the journal 109 and the bearing 108.
However, when the driving motor 101 stops in the conventional hermetic compressor, most of the oil which is located between the journal 109 and the bearing 108 flows downward by its own weight, so that little oil remains therebetween. Therefore, when the compressor restarts its operation, non-lubricating friction generates between the journal 109 and the bearing 108 until the oil is supplied therebetween through the oil pickup tube 116, thereby increasing abrasion of the journal 109 and the bearing 108, making a starting rotation of the rotating shaft 106 unstable and generating noises.